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Biologists at Fred Hutchinson Cancer Research Center discovered that a single mutation in a flu virus can give it the power to escape 90% of one person’s antibody immunity, but not another’s.
Immunity can be acquired either actively or passively. Immunity is acquired actively when a person is exposed to foreign substances and the immune system responds. Passive immunity is when antibodies are transferred from one host to another. Both actively acquired and passively acquired immunity can be obtained by natural or artificial means.
Mammalian influenza viruses tend to be labile, but they can survive several hours in a host’s mucus. [57] Avian influenza virus can survive for 100 days in distilled water at room temperature and for 200 days at 17 °C (63 °F). The avian virus is inactivated more quickly in manure but can survive for up to two weeks in feces on cages.
The result: “56% of one community-obtained virus was similar to one component of the vaccine and 100% of a second flu virus was similar to a different vaccine component,” Dr. Shah says.
These pandemics, in contrast to seasonal influenza, are caused by antigenic shifts involving animal influenza viruses. To date, all known flu pandemics have been caused by influenza A viruses, and they follow the same pattern of spreading from an origin point to the rest of the world over the course of multiple waves in a year.
What are the different types of influenza virus? There are four different types of influenza virus: A, B, C, and D. Influenza C usually causes only mild illness while D mostly affects animals ...
He further formalised the theory in his 1959 book The Clonal Selection Theory of Acquired Immunity. He explained immunological memory as the cloning of two types of lymphocyte. One clone acts immediately to combat infection whilst the other is longer lasting, remaining in the immune system for a long time and causing immunity to that antigen.
An individual's immunity can be acquired via a natural infection or through artificial means, such as vaccination. [51] When a critical proportion of the population becomes immune, called the herd immunity threshold (HIT) or herd immunity level (HIL), the disease may no longer persist in the population, ceasing to be endemic. [5] [26]